Rechargeable lithium-ion batteries have become an important source of power for many applications due to their relatively low mass and high energy density. Rechargeable lithium-ion batteries have potential use as high power devices in large-scale applications such as electric vehicles (EV) and hybrid electric vehicles (HEV).
Graphite/LiCoO2 is the most commonly used electrochemical couple in lithium-ion batteries, where the LiCoO2 is at the cathode and the graphite is at the anode. Current, commercially available, lithium-ion batteries exhibit several weaknesses including:                i. at full charge, lithiated graphite (LiC6) electrodes are highly reactive because operational voltages are very close to that of metallic lithium; and        ii. the thermal degradation of passivation films formed at the graphite electrode, commonly referred to as solid electrolyte interfaces (SEI), occurs at temperatures as low as 100° C., and can easily lead to thermal runaway as a result of external heat and/or internal heating during the charging process. Both the operational voltage close to metallic lithium and the thermal degradation present safety concerns.        
To overcome thermal runaway, battery manufacturers may incorporate a variety of components into their Li-ion cells, including electrolyte additives, shutdown separators, positive thermal coefficient (PTC) devices, or combinations of these safety components. The high expenses accompanying the introduction of these safety measures in lithium-ion batteries will likely reduce the penetration of this technology into industrial applications by cost-conscious developers.
In order to cost effectively address the safety limitations of lithium-ion cells, alternative anodes to graphite have been suggested. Alternatives such as the spinel Li4Ti5O12, which operates at 1.5 V vs. Li0, may provide an electrode system with better safety characteristics. Indeed, at this voltage the Li4Ti5O12 anode will not form the conventional SEI films which usually form in graphite, because of the reduction of the organic species occurs at potentials less than one volt. In addition, unlike graphite anodes, no volume change is expected during the insertion of three lithium atoms into the spinel structure of Li4Ti5O12, which leads to the formation of a rock-salt type Li7Ti5O12 material with a zero-strain structural character. Furthermore, batteries based on Li4Ti5O12 should exhibit good low temperature performance as no lithium plating can occur on Li4Ti5O12 due to its potential being 1.5V higher than Li/Li+. Moreover, the material can be coupled with a 4V electrode such as LiCoO2, LiNiO2, or LiMn2O4 to provide a system operating at 2.5 V, which is twice that of a nickel-metal hydride cell.
However, anodes based on Li4Ti5O12 exhibit intrinsically poor electronic conductivity. Practical battery systems require the use of electrodes that have both good ionic conductivity, to allow rapid lithium-ion diffusion within the host, and good electronic conductivity, to transfer electrons from the host to the external circuit during the charging and discharging processes.
A need exists for electrode materials for high power and high energy lithium battery systems, that can provide high energy and high power with long cycle life and long calendar life, without the safety challenges of previously known systems.